1. Field of the Invention
The present invention relates to a polyphenylene ether resin composition. More particularly, the pre-sent invention is concerned with a polyphenylene ether resin composition comprising a polyphenylene ether, wherein the polyphenylene ether has a polymer chain comprising specific recurring units and has the following characteristics: when the polyphenylene ether is analyzed by proton nuclear magnetic resonance spectroscopy (1H-NMR), the polyphenylene ether exhibits a triplet signal having a specific intensity at 3.55 ppm; when the polyphenylene ether is analyzed by ultraviolet-visible spectroscopy, the polyphenylene ether exhibits an absorbance of from 0.01 to 0.40 at a wavelength of 480 nm; and the polyphenylene ether has a weight average molecular weight of from 30,000 to 100,000.
The polyphenylene ether resin composition of the present invention not only has excellent properties comparable to those of conventional polyphenylene ether resin compositions, especially with respect to heat resistance, electrical characteristics, acid resistance, alkali resistance, dimensional stability, low specific gravity and low water absorption, but also exhibits an excellent balance of fluidity, chemicals resistance (i.e., resistance to organic solvents and oils) and appearance of a molded article obtained therefrom as well as excellent color of a molded article obtained therefrom. Therefore, the polyphenylene ether resin composition of the present invention can be advantageously used in various application fields, such as thin-walled parts and oil-resistant parts (e.g., electric and electronic parts and automobile parts) which stay intact even when oils adhere thereto.
2. Prior Art
A polyphenylene ether inherently exhibits not only excellent heat resistance, electrical characteristics, acid resistance, alkali resistance and dimensional stability, but also a low specific gravity, a low water absorption and the like, so that a polyphenylene ether has conventionally been widely used. Further, there are also known various types of polyphenylene ethers having improved properties with respect to chemicals resistance (i.e., resistance to organic solvents and oils), appearance of a molded article obtained therefrom, and the like. However, a polyphenylene ether has not only a high glass transition temperature but also a property that the molecular weight increases during the heat-melting thereof, so that the polyphenylene ether is defective in fluidity, that is, the polyphenylene ether is difficult to mold by melting. For alleviating this defect, it has conventionally been attempted to use a polyphenylene ether in the form of a composition thereof with another material.
For example, a polyphenylene ether has high compatibility with a polystyrene, so that it has been attempted to produce an alloy of the polyphenylene ether with a styrene polymer resin to thereby improve the fluidity of the polyphenylene ether. However, such an alloy cannot exhibit any longer not only excellent heat resistance inherently possessed by the polyphenylene ether, but also excellent chemicals resistance and appearance of a molded article obtained therefrom.
For improving the fluidity of a polyphenylene ether, it has also been attempted to use a polyphenylene ether resin composition which is produced by mixing a first polyphenylene ether having a molecular weight sufficient to mold and a second polyphenylene ether having a low molecular weight. In this resin composition, the fluidity is improved due to the shift of the molecular weight distribution of the polyphenylene ether toward the low molecular weight region.
The above-mentioned attempt is described, for example, in the Examples of Examined Japanese Patent Application Publication No. Sho 45-25992 and in Japanese Patent No. 2648887 (corresponding to U.S. Pat. No. 5,081,185), each of which proposes a resin composition comprising two types of polyphenylene ethers having different solution viscosities. By the above-mentioned attempt, on one hand, the polyphenylene ether is improved with respect to fluidity, but on the other hand, it is inevitably diminished with respect to some properties (such as chemicals resistance) as well as a molded article appearance. Further, the attempt is disadvantageous in that, for individually producing the above-mentioned two types of polyphenylene ethers having different solution viscosities and mixing these polyphenylene ethers, it is necessary to employ an extremely complicated apparatus.
As mentioned above, in the prior art, there has been a technical dilemma in that, when it is attempted to improve the fluidity of a polyphenylene ether, other important properties (such as chemicals resistance and molded article appearance) inherently possessed by the polyphenylene ether are inevitably diminished.
Therefore, it has been desired to develop a polyphenylene ether resin composition which not only retains excellent properties inherently possessed by conventional polyphenylene ethers, but also exhibits an excellent balance of fluidity, chemicals resistance and molded article appearance.